Foundation pit supporting method

Abstract

The invention belongs to the technical field of foundation pit supporting, discloses a foundation pit supporting method, and aims to solve the problem of local collapse of a rock-soil body between rear-row piles after excavation of a deep foundation pit. The method comprises the following steps: (1) determining the position of a front-row support pile; (2) constructing front-row support piles and rear-row support piles; (3) excavating inter-pile soil between the front-row support piles and the rear-row support piles to form an excavation area; (4) constructing micro grouting steel pipe piles at the bottom of the excavation area; (5) driving anchor rods into the soil among the piles of each support pile in the rear row of support piles, and constructing an embedded connecting beam; (6) backfilling an excavation area between the front-row support piles and the rear-row support piles, and tamping; and (7) excavating the foundation pit. According to the method, the soil body behind the deep foundation pit can be effectively prevented from collapsing between the row piles, so that it is ensured that collapse of a larger area cannot be caused by local collapse, and the safety and the construction progress of foundation pit excavation are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation pit support, and in particular relates to a foundation pit support method. Background Art

[0002] Foundation pit support is an essential project before building construction. Foundation pit support involves the safety and progress efficiency of subsequent construction. Foundation pit support is divided into shallow foundation pit support and deep foundation pit support according to the depth of the foundation pit. In comparison, deep foundation pit support is more difficult because it involves factors such as changes in stratum structure, the influence of groundwater level, and sudden changes in soil lateral pressure.

[0003] There are also many technical documents on deep foundation pit support in the prior art. For example, the patent with application number 201510552809X discloses a pile-anchor support method for deep foundation pits and ultra-deep foundation pits, which includes the following steps: a. Determine the cohesion c and internal friction angle of the soil sample of the embedded section of the support pile; b. Calculate the deformation bearing capacity of the embedded section of the support pile and the soil reaction force ps at the corresponding position; c. Compare the size with ps; d. If the size parameters of the support pile are adjusted or the depth of the embedded section is increased; e. Repeat steps b to d until f. Construct according to the size of the support pile and the depth of the embedded section determined in the above steps.

[0004] For example, the patent with application number 2024109010464 discloses a deep foundation pit support structure and a deep foundation pit construction method, including a support mechanism and a supporting mechanism. The supporting mechanisms are arranged in pairs and supported on the relative walls of the deep foundation pit. The supporting mechanism includes a first support plate assembly and a second support plate assembly that can rotate around the same axis. The first support plate assembly is used to support the side wall surface of the deep foundation pit and can extend along the side wall surface. The second support plate assembly is used to support the bottom wall surface of the deep foundation pit and can extend along the bottom wall surface, so that it can adapt to foundation pits of different specifications. The supporting mechanism is connected to the first support plate assembly, and the relatively arranged supporting mechanisms provide a tightening force through a hydraulic telescopic rod, thereby improving the overall safety of the support structure at the corresponding position, and monitoring the local stress changes of the deep foundation pit through a detection device arranged on the supporting mechanism, so that timely prevention of local stress mutations can be taken in advance.

[0005] For another example, the patent with application number 2023109728969 discloses a deep foundation pit support structure and a deep foundation pit construction method, including a fixed seat symmetrically installed on the ground at the edge of the deep foundation pit, a slope support mechanism is arranged between the opposite sides of the fixed seat for covering and supporting the slope surface of the deep foundation pit, and the slope support mechanism includes a flip shaft rotatably installed inside the front fixed seat. The present invention relates to the field of deep foundation pit support technology. The deep foundation pit support structure and the deep foundation pit construction method are provided with a slope support mechanism, and the driving operation of the pneumatic component is utilized to enable the flip shaft to drive the support plate to perform a support operation on the slope, and the upper linkage component drives the plug-in unit to always maintain a vertical state, thereby completing the fixation after the support operation, so that the bottom installation can be kept in a vertical state before fixation, thereby improving the support and fixation operation on the slope of the deep foundation pit layer, and improving the safety of subsequent deep foundation pit excavation.

[0006] For example, the patent application number 2016103773195 discloses a deep foundation pit construction method for controlling foundation pit deformation under a supporting system, comprising: excavating earth at the supporting part of the supporting system of the deep foundation pit; constructing a first cushion layer at the supporting part; constructing a first foundation bottom plate at the supporting part to close the supporting part; excavating earth at the non-supporting part of the supporting system of the deep foundation pit; constructing a second cushion layer at the non-supporting part; constructing a second foundation bottom plate at the non-supporting part to close the non-supporting part, thereby closing the entire deep foundation pit.

[0007] As exemplified above, deep foundation pit support mainly adopts a support system for the foundation pit formed by combining rows of piles, underground continuous walls, cement soil piles, anchor rods, soil nails, steel pipe piles and internal supports.

[0008] However, the current foundation pit support system still has the following problems in actual use: after the foundation pit is excavated, the lateral pressure of the soil changes greatly. Even if anchor rods and steel mesh are used to support the excavated soil, there is still the problem of partial rock and soil collapse. In particular, when the foundation pit encounters soft strata and is soaked in rain for a long time, local area collapse (the soil between the piles, often called inter-pile soil) is more serious. Although this local collapse generally does not cause safety accidents, the support effect of the piles on the soil will be reduced after the local collapse. With the reduction of the supporting effect of the piles, it will gradually induce a larger area of ​​collapse. Therefore, during the foundation pit excavation process, after the local collapse occurs, it has to be reinforced again to prevent the induction of a larger area of ​​collapse. Summary of the invention

[0009] In order to solve the problem of local collapse of rock and soil between rows of piles after deep foundation pit excavation, the present invention provides a foundation pit support method, which can effectively prevent the soil from collapsing between the rows of piles after the deep foundation pit, thereby ensuring that local collapse will not cause collapse of a larger area, thereby ensuring the safety of foundation pit excavation and construction progress.

[0010] In order to solve the technical problem, the technical solution adopted by the present invention is:

[0011] A foundation pit supporting method, characterized by comprising:

[0012] (1) Measure and lay out to determine the position of the front row support piles;

[0013] (2) constructing the front row of supporting piles, and then constructing the rear row of supporting piles after the front row of supporting piles are constructed, with a distance between the rear row of supporting piles and the front row of supporting piles;

[0014] (3) After the construction of the rear row of supporting piles is completed, the soil between the front row of supporting piles and the rear row of supporting piles is excavated to form an excavation area. The excavation depth of the soil between the front row of supporting piles and the rear row of supporting piles shall not be less than one fifth of the foundation pit depth;

[0015] (4) After the soil excavation between the front row support piles and the rear row support piles is completed, micro grouting steel pipe piles are constructed at the bottom of the excavation area;

[0016] (5) After the construction of the micro-grouting steel pipe piles is completed, anchor rods are driven into the soil between the piles of each of the rear supporting piles, and a pre-buried connecting beam is constructed between the front supporting piles and the rear supporting piles. The pre-buried connecting beam is located at the bottom of the excavation area and is used to connect the front supporting piles and the rear supporting piles;

[0017] (6) After the anchor rods and pre-buried connecting beams of step (5) are completed, the excavated area between the front row supporting piles and the rear row supporting piles is backfilled and compacted;

[0018] (7) Excavation of foundation pit: During the excavation of foundation pit, concrete shall be sprayed on the soil between each supporting pile of the front row of supporting piles and anchor rods or soil nails shall be implanted to stabilize the soil between the piles.

[0019] In some embodiments, the construction of the embedded connecting beam includes: first, drilling holes on the front row supporting piles and the rear row supporting piles and implanting steel bars, then connecting the implanted steel bars to the skeleton of the embedded connecting beam, and finally pouring concrete to form the embedded connecting beam.

[0020] In some embodiments, the implantation positions of the anchor rods or soil nails of the front row of supporting piles are staggered with the positions of the anchor rods of the rear row of supporting piles.

[0021] In some embodiments, the anchor rods on the rear row of supporting piles extend obliquely downward into the rock and soil.

[0022] In some embodiments, a guide tube is provided on the outer periphery of the free section of the anchor rod of the rear row supporting piles, and strip holes are arranged in sections on the guide tube. The strip holes of the same section are evenly opened on the circumferential wall of the guide tube, and there is a spacing between the strip holes of each section.

[0023] In some embodiments, the guide tube is sleeved on the periphery of the anchor reinforcement of the anchor rod and is implanted into the anchor hole along with the anchor reinforcement.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] Compared with the existing double-row pile support system, the foundation pit support method of the present invention, on the one hand, utilizes pre-buried connecting beams to replace the connecting beams in the existing double-row pile support system (that is, the connecting beams of the existing double-row pile support system are all connected to the front crown beam and the rear crown beam). The design of the pre-buried connecting beam can greatly improve the structural rigidity of the double-row pile support system; on the other hand, the micro-grouting steel pipe piles at the bottom of the excavation area between the front row supporting piles and the rear row supporting piles can greatly improve the bearing capacity of the soil between the front row supporting piles and the rear row supporting piles, thereby further improving the structural rigidity between the front row supporting piles and the rear row supporting piles, forming an "H"-shaped double-row pile support system with higher structural rigidity, which can greatly improve the support capacity for the foundation pit, and thus prevent local collapse after the foundation pit excavation.

[0026] At the same time, the "H"-shaped double-row pile support system formed by the embedded connecting beams and micro-grouting steel pipe piles, the front supporting piles and the rear supporting piles improves the structural rigidity between the front supporting piles and the rear supporting piles. Therefore, in the actual construction process, the distance between the front supporting piles and the rear supporting piles can be appropriately expanded, so that the front supporting piles and the rear supporting piles can fully play their supporting role.

[0027] In the prior art, the spacing between the front row support piles and the rear row support piles is generally between 2d and 5d (where d is the diameter of the row piles). The main reason is that the double-row pile support system formed by the front row support piles and the rear row support piles is not rigid enough (the connecting beam is connected to the crown beam of the front row support piles and the rear row support piles), so that the influence range of the front row support piles and the influence range of the rear row support piles overlap in a large area, so that the front row support piles and the rear row support piles cannot give full play to their respective support capabilities. The present invention uses pre-buried connecting beams and micro-grouting steel pipe piles to improve the rigidity between the front row support piles and the rear row support piles, so that the spacing between the front row support piles and the rear row support piles can be increased, thereby minimizing the overlap area of ​​the influence range of the front row support piles and the rear row support piles, ensuring that the front row support piles and the rear row support piles can give full play to their reinforcement influence range, and ultimately improve the foundation pit support capacity, effectively avoiding the problem of local collapse after foundation pit excavation.

[0028] The present invention can not only improve the rigidity of the front row support piles and the rear row support piles by arranging the micro grouting steel pipe at the bottom of the excavation area, but also has the following principle: after the micro grouting steel pipe piles are implanted into the excavation area, the soil in the excavation area can be grout-reinforced, so that the reinforced rock and soil in the excavation area and the micro grouting steel pipe piles can be used to transmit the force between the front row support piles and the rear row support piles. For example, when the rear row support piles cannot withstand the soil pressure alone, the rear row support piles transmit the force to the reinforced rock and soil in the excavation area, and then to the rear row support piles, so that the rear row support piles and the front row support piles can withstand the soil pressure together. And after the micro grouting steel pipe piles are constructed in the excavation area, since the micro grouting steel pipe itself has a certain depth, the middle section area of ​​the front row support piles and the rear row support piles can transmit the force to each other, so that the front row support piles and the rear row support piles can share the force synergistically, so as to achieve the purpose of improving the support capacity of the double row pile support system.

[0029] The present invention is applicable to foundation pit support in areas with soft strata, rainy areas, and areas with expansive soil. When the traditional double-row pile support system is used for foundation pit support in areas with soft strata and rainy areas, the rigid strength between the front row support piles and the rear row support piles mainly depends on the connecting beam because the soft strata transmit weak forces, and the connecting beam is arranged at the top of the row of piles, so that the transmission of forces between the front row support piles and the rear row support piles is relatively small, which greatly reduces the support capacity. Similarly, for rainy areas, due to excessive rainwater infiltration into the soil between the front row support piles and the rear row support piles, the shear resistance between the front row support piles and the rear row support piles is greatly weakened, which in turn affects the transmission of forces between the front row support piles and the rear row support piles, and ultimately leads to a weakening of the support capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The schematic diagram of the structure of an existing double-row pile support system is shown in FIG. Figure 1 Includes 1A and 1B; Figure 1 A is a schematic diagram of the double-row pile support system during normal support. Figure 1 B is a schematic diagram showing the state when the rear row support piles cannot withstand the lateral pressure of the soil, and the soil between the front row support piles and the rear row support piles cannot transmit the force to the front row support piles, causing the rear row support piles to tilt;

[0031] Figure 2 A structural schematic diagram of an embodiment of an "H"-shaped double-row pile support system formed by the present invention;

[0032] Figure 3 It is a cross-sectional structural schematic diagram of the free section of the anchor rod implanted between the piles of the rear row support piles of the present invention;

[0033] Figure 4It is a schematic structural diagram of the guide tube of the present invention.

[0034] Markings in the figure: 1. Front row supporting piles, 2. Front crown beam, 3. Rear row supporting piles, 4. Rear crown beam, 5. Connecting beam, 6. Excavation area, 7. Micro grouting steel pipe piles, 8. Embedded connecting beam, 9. Anchor rods, 91. Anchor rod steel bars, 92. Grouting pipes, 93. Centering brackets, 94. Guide pipes, 941. Strip holes. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with embodiments, which are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in the field without creative work are all within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In conjunction with the accompanying drawings, the foundation pit supporting method of the present invention comprises:

[0038] (1) Measure and lay out to determine the position of the front row support piles 1; in the specific implementation process, the selection of the diameter of the front row support piles 1 is mainly determined based on the bending moment size and deformation requirements to achieve the requirements of force and economic rationality, while also meeting the requirements of construction conditions, and the center distance of the front row support piles 1 should not be greater than 2.0 times the pile diameter, etc. The determination of the spacing between the piles must also consider the stability requirements of the soil between the piles. According to construction experience, for large pile diameters or clay soils, the net distance between the piles is usually within 900mm; for small pile diameters or sandy soils, the net distance between the piles is usually within 600mm. Therefore, the construction of the piles is understandable to those skilled in the art and will not be elaborated here.

[0039] (2) Construct the front row support piles 1, and after the front row support piles 1 are constructed, construct the rear row support piles 3, with a spacing between the rear row support piles 3 and the front row support piles 1. After the front row support piles 1 are constructed, the front crown beam 2 should also be constructed, the width of the crown beam should not be less than the pile diameter, and the height should not be less than 0.6 times the pile diameter, and the front crown beam 2 is used to connect the front row support piles 1 to form a whole.

[0040] (3) After the construction of the rear row supporting piles 3 is completed, the soil between the front row supporting piles 1 and the rear row supporting piles 3 is excavated to form an excavation area 6, and the excavation depth of the soil between the front row supporting piles 1 and the rear row supporting piles 3 is not less than one fifth of the foundation pit depth. As a matter of course, after the construction of the rear row supporting piles 3 is completed, the rear crown beam 4 should be constructed to connect the rear row supporting piles 3 to each other. The construction of the crown beams (front crown beams 2 and rear crown beams 4) also belongs to the prior art, which can be understood and understood by those skilled in the art, and will not be elaborated here.

[0041] During the specific implementation process, in order to prevent the soil between the front row supporting piles 1 and the soil between the rear row supporting piles 3 from falling off, concrete should be sprayed in time during the excavation of the excavation area 6. If necessary, steel mesh should be laid first and then concrete should be sprayed.

[0042] During the excavation of the soil between the front row of supporting piles 1 and the rear row of supporting piles 3 (i.e., during the excavation of excavation area 6), when the soil between the front row of supporting piles 1 and the rear row of supporting piles 3 is a soft stratum, the excavation depth of the soil between the front row of supporting piles 1 and the rear row of supporting piles 3 can be appropriately increased. However, based on construction cost considerations, the excavation depth of the soil between the front row of supporting piles 1 and the rear row of supporting piles 3 (i.e., the depth of excavation area 6) should not be greater than one quarter of the foundation pit depth.

[0043] (4) After the excavation of the soil between the front row supporting piles 1 and the rear row supporting piles 3 is completed, the micro-grouting steel pipe piles 7 are constructed at the bottom of the excavation area 6; in the specific construction process, the micro-grouting steel pipe piles 7 are arranged in a plum blossom shape between the front row supporting piles 1 and the rear row supporting piles 3. Among them, the construction process of the micro-grouting steel pipe piles 7 belongs to the existing technology, which mainly includes drilling holes-implanting steel flower pipes-grouting and pouring-secondary pouring. Those skilled in the art can understand and comprehend it, and it will not be repeated here.

[0044] (5) After the construction of the micro-grouting steel pipe piles 7 is completed, anchor rods 9 are driven into the soil between the piles of each of the rear supporting piles 3, and the pre-embedded connecting beams 8 are constructed between the front supporting piles 1 and the rear supporting piles 3. In the specific implementation process of the pre-embedded connecting beams 8, holes are firstly drilled on the front supporting piles 1 and the rear supporting piles 3 and steel bars are implanted, and then the implanted steel bars are connected to the skeleton of the pre-embedded connecting beams 8, and finally concrete is poured to form the pre-embedded connecting beams 8. The pre-embedded connecting beams 8 are arranged at the bottom of the excavation area 6.

[0045] (6) After the anchor rods 9 and the embedded connecting beams 8 of step (5) are completed, the excavated area 6 between the front row support piles 1 and the rear row support piles 3 is backfilled and compacted. During the compaction process, layered rolling compaction should be adopted, and after the compaction process, the soil density of the excavated area shall not be lower than the density of the original soil.

[0046] (7) Excavation of foundation pit: During the excavation of foundation pit, concrete shall be sprayed on the soil between each supporting pile of the front row supporting piles 1 and anchor rods 9 or soil nails shall be implanted to stabilize the soil between the piles.

[0047] Compared with the existing double-row pile support system, the foundation pit support method of the present invention, on the one hand, uses pre-buried connecting beams to replace the connecting beams in the existing double-row pile support system (that is, the connecting beams of the existing double-row pile support system are all connected to the front crown beam and the rear crown beam), and the design of the pre-buried connecting beam can greatly improve the structural rigidity of the double-row pile support system; on the other hand, the micro-grouting steel pipe piles at the bottom of the excavation area between the front row supporting piles and the rear row supporting piles can greatly improve the bearing capacity of the soil between the front row supporting piles and the rear row supporting piles, thereby further improving the structural rigidity between the front row supporting piles and the rear row supporting piles, forming an "H"-shaped double-row pile support system with higher structural rigidity, which can greatly improve the support capacity of the foundation pit, and thus prevent the occurrence of local collapse after the foundation pit is excavated. Thereby ensuring that a larger area of ​​collapse will not be caused due to local collapse, and ensuring the safety and construction progress of the foundation pit excavation.

[0048] At the same time, the "H"-shaped double-row pile support system formed by the embedded connecting beams and micro-grouting steel pipe piles, the front supporting piles and the rear supporting piles improves the structural rigidity between the front supporting piles and the rear supporting piles. Therefore, in the actual construction process, the distance between the front supporting piles and the rear supporting piles can be appropriately expanded, so that the front supporting piles and the rear supporting piles can fully play their supporting role.

[0049] In the prior art, the spacing between the front row support piles and the rear row support piles is generally between 2d and 5d (where d is the diameter of the row piles). The main reason is that the double-row pile support system formed by the front row support piles and the rear row support piles is not rigid enough (the connecting beam is connected to the crown beam of the front row support piles and the rear row support piles), so that the influence range of the front row support piles and the influence range of the rear row support piles overlap in a large area, so that the front row support piles and the rear row support piles cannot give full play to their respective support capabilities. The present invention uses pre-buried connecting beams and micro-grouting steel pipe piles to improve the rigidity between the front row support piles and the rear row support piles, so that the spacing between the front row support piles and the rear row support piles can be increased, thereby minimizing the overlap area of ​​the influence range of the front row support piles and the rear row support piles, ensuring that the front row support piles and the rear row support piles can give full play to their reinforcement influence range, and ultimately improve the foundation pit support capacity, effectively avoiding the problem of local collapse after foundation pit excavation.

[0050] The present invention can not only improve the rigidity of the front row support piles and the rear row support piles by arranging the micro grouting steel pipe at the bottom of the excavation area, but also has the following principle: after the micro grouting steel pipe piles are implanted into the excavation area, the soil in the excavation area can be grout-reinforced, so that the reinforced rock and soil in the excavation area and the micro grouting steel pipe piles can be used to transmit the force between the front row support piles and the rear row support piles. For example, when the rear row support piles cannot withstand the soil pressure alone, the rear row support piles transmit the force to the reinforced rock and soil in the excavation area, and then to the rear row support piles, so that the rear row support piles and the front row support piles can withstand the soil pressure together. And after the micro grouting steel pipe piles are constructed in the excavation area, since the micro grouting steel pipe itself has a certain depth, the middle section area of ​​the front row support piles and the rear row support piles can transmit the force to each other, so that the front row support piles and the rear row support piles can share the force synergistically, so as to achieve the purpose of improving the support capacity of the double row pile support system.

[0051] The present invention is applicable to foundation pit support in areas with soft strata, rainy areas, and areas with expansive soil. When the traditional double-row pile support system is used for foundation pit support in areas with soft strata and rainy areas, the rigid strength between the front row support piles and the rear row support piles mainly depends on the connecting beam because the soft strata transmit weak forces, and the connecting beam is arranged at the top of the row of piles, so that the transmission of forces between the front row support piles and the rear row support piles is relatively small, which greatly reduces the support capacity. Similarly, for rainy areas, due to excessive rainwater infiltration into the soil between the front row support piles and the rear row support piles, the shear resistance between the front row support piles and the rear row support piles is greatly weakened, which in turn affects the transmission of forces between the front row support piles and the rear row support piles, and ultimately leads to a weakening of the support capacity.

[0052] In some embodiments, the implantation position of the anchor rod 9 or soil nail of the front row supporting pile 1 is staggered with the position of the anchor rod 9 of the rear row supporting pile 3. In the specific implementation process, since the present invention pre-arranges the anchor rod 9 in the excavation area 6 (the area between the front row supporting piles and the rear row supporting piles); and the micro-grouting steel pipe piles 7 arranged in the excavation area 6 can reinforce the excavation area 6, it is possible to increase the anchoring force of a single anchor rod 9 or soil nail on the front row supporting pile 1. In summary, after the foundation pit is excavated, the number of implanted anchor rods 9 or soil nails of the front row supporting piles 1 can be appropriately reduced to reduce construction costs.

[0053] In some embodiments, the anchor rods 9 on the rear row of supporting piles 3 extend obliquely downward into the rock and soil.

[0054] In some embodiments, the outer periphery of the free section of the anchor rod 9 of the rear row support pile 3 is provided with a guide tube 94, and the guide tube 94 is provided with strip holes 941 in sections, and each strip hole 941 of the same section is evenly opened on the circumferential wall of the guide tube 94, and there is a spacing between each section of the strip holes 941. The strip holes 91 of the guide tube 94 allow the injected slurry to smoothly combine with the rock and soil around the anchor hole, so that the slurry and the rock and soil form a whole; at the same time, since there is a spacing between each section of the strip holes, the section of the guide tube 94 without the strip holes 941 can be used to gradually drain the groundwater in the rock and soil, so that the groundwater moves obliquely downward along the direction of the anchor rod 9, thereby reducing the flow of groundwater toward the excavation area and the direction of the front row support pile 1. In addition, since the anchoring effect of the anchor rod 9 mainly comes from the anchoring section of the anchor rod 9, even if the guide tube 94 of the free section of the anchor rod 9 plays a certain drainage role, it will not affect the anchoring force of the entire anchor rod 9.

[0055] In the specific implementation process, although the slurry can play a certain blocking role in the gaps in the rock and soil around the anchor hole after being injected into the anchor hole, this blocking effect is limited (first, it cannot ensure that the periphery of the position is blocked, and second, the slurry that penetrates into the rock and soil has a limited impact range). Therefore, the present invention utilizes the role of the strip hole 941 to ensure the combination with the surrounding rock and soil, and at the same time utilizes the guide pipe 94 in the section without the strip hole to play a certain drainage role, so that the groundwater can gradually penetrate downward along the outer wall of the guide pipe 94, thereby directing the groundwater away from the foundation pit, reducing the impact of the groundwater on the excavation area 6, the front row of support piles 1 and the foundation pit.

[0056] In some embodiments, the guide tube 94 is sleeved on the periphery of the anchor reinforcement 91 of the anchor rod and is implanted into the anchor hole along with the anchor reinforcement 91. In the specific implementation process, the anchor reinforcement 91 and the guide tube 94 are fixed in the anchor hole by the centering bracket 93, and the grouting pipe 92 is fixed on the centering bracket 93, so that the grouting operation in the anchor hole is performed by the grouting pipe 92, which can be understood by those skilled in the art and will not be described in detail here.

Claims

1. A foundation pit support method, characterized in that: include: (1) measuring and setting out to determine the position of the front row of support piles (1); (2) constructing the front row of supporting piles (1), and after the construction of the front row of supporting piles (1) is completed, constructing the rear row of supporting piles (3), wherein there is a distance between the rear row of supporting piles (3) and the front row of supporting piles (1); (3) After the construction of the rear row supporting piles (3) is completed, the soil between the front row supporting piles (1) and the rear row supporting piles (3) is excavated to form an excavation area (6), and the excavation depth of the soil between the front row supporting piles (1) and the rear row supporting piles (3) is not less than one fifth of the foundation pit depth; (4) After the soil excavation between the front row supporting piles (1) and the rear row supporting piles (3) is completed, micro grouting steel pipe piles (7) are constructed at the bottom of the excavation area (6); (5) After the construction of the micro-grouting steel pipe piles (7) is completed, anchor rods (9) are driven into the soil between the piles of each of the rear supporting piles (3), and a pre-buried connecting beam (8) is constructed between the front supporting piles (1) and the rear supporting piles (3). The pre-buried connecting beam (8) is located at the bottom of the excavation area (6) and is used to connect the front supporting piles (1) and the rear supporting piles (3); (6) After the anchor rods (9) and the pre-buried connecting beams (8) of step (5) are completed, the excavated area (6) between the front row of supporting piles (1) and the rear row of supporting piles (3) is backfilled and compacted; (7) Excavation of foundation pit: During the excavation of foundation pit, concrete shall be sprayed on the soil between each support pile of the front row support piles (1) and anchor rods (9) or soil nails shall be planted to stabilize the soil between the piles.

2. The foundation pit supporting method according to claim 1, characterized in that: The construction of the embedded connecting beam (8) includes: firstly, drilling holes on the front row supporting piles (1) and the rear row supporting piles (3) and implanting steel bars, then connecting the implanted steel bars with the skeleton of the embedded connecting beam (8), and finally pouring concrete to form the embedded connecting beam (8).

3. The foundation pit supporting method according to claim 1, characterized in that: The implantation positions of the anchor rods (9) or soil nails of the front row of supporting piles (1) and the positions of the anchor rods (9) of the rear row of supporting piles (1) are staggered with each other.

4. The foundation pit supporting method according to claim 1, characterized in that: The anchor rods (9) on the rear row of supporting piles (9) extend obliquely downward into the rock and soil.

5. The foundation pit supporting method according to claim 1, characterized in that: A guide tube (94) is sleeved on the outer periphery of the free section of the anchor rod (9) of the rear row support pile (3), and strip holes (941) are arranged in sections on the guide tube (94). The strip holes (941) of the same section are evenly arranged on the circumferential wall of the guide tube (94), and there is a spacing between the strip holes (941) of each section.

6. The foundation pit supporting method according to claim 1, characterized in that: The guide tube (941) is sleeved on the periphery of the anchor rod reinforcement (91) of the anchor rod (9) and is implanted into the anchor hole along with the anchor rod reinforcement (91).

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